The six global powers will discuss ways to reach a comprehensive nuclear deal with Iran on the sidelines of the United Nations General Assembly in New York in September, the European Union's foreign policy chief said on Saturday.

Catherine Ashton, the EU's top diplomat, is expected to continue to lead nuclear negotiations with Iran even as she leaves her EU job at the end of October.

"There are ongoing discussions on that," Ashton told a news conference when asked if nuclear talks would take place in New York around mid-September.

"We will use the opportunity of the General Assembly in New York to also do that," Ashton, speaking at the end of a two-day informal gathering of EU foreign ministers in Milan that discussed the situation in Ukraine, Iraq and the Middle East.

Ashton is due to meet Iran Iranian Foreign Minister Mohammad Javad Zarif in Brussels on Monday.